Duas populações do complexo Astyanax scabripinnisisoladas por uma queda d´água de mais de 100 metros de altura e localizadas em diferentes altitudes do mesmo rio (662 m e 1850 m a.s.l.) foram comparadas através de dados de reprodução, cariótipo, morfometria geométrica, morfologia dentária, e número de raios da nadadeira anal, de modo a testar a hipótese de especiação entre as duas populações. Os resultados de morfometria geométrica mostraram diferenças entre as populações. A análise da função discriminante (DFA) e a análise de variância canônica (CVA) demonstraram a presença de dimorfismo sexual. Caracteres sexuais secundários, como ganchos em raios da nadadeira anal dos machos, estão ausentes na população de menor altitude. Ambas as populações têm a mesma macro estrutura cariotípica, exceto pela ausência de cromossomos B na população de menor altitude. A hibridação in situ mostrou diferenças para ambos os marcadores (rDNA 18S e rDNA 5S), e os dados de reprodução sugerem isolamento reprodutivo pré-zigótico entre as duas populações. Os dados mostram ausência de fluxo gênico, indicando que ocorreu um processo de especiação incipiente, o que leva as duas populações seguirem vias evolutivas independentes.

Two populations of the Astyanax scabripinniscomplex, isolated by a waterfall with over 100 meters depth and inhabiting different altitudes of the same river (1850 m a.s.l. and 662 m a.s.l.) were compared in reproductive data, geometric morphometry, tooth morphology, anal-fin rays counts, and karyotype, in order to test the hypothesis of speciation between the two populations. The results in the geometric morphometry analysis showed differences between the populations. Discriminant function analysis (DFA) and canonical variance analysis revealed sexual dimorphism. Secondary sexual characters, such as hooks in the anal fin rays of the males are absent in the lower altitude population. Both populations had the same macro karyotype structure, except for the absence of B chromosomes in the lower altitude population. The fluorescence in situ hybridization showed differences for both markers (18S rDNA and 5S rDNA), and reproductive data suggests pre-zygotic reproductive isolation among the two populations. The data showed the absence of gene flow, indicating that an incipient speciation process has occurred, which leads the two populations to follow independent evolutionary pathways.

Lithobates catesbeianus (Shaw, 1802) is an invasive anuran introduced in Brazil that is associated with the displacement and the decline of populations of native species worldwide. There is evidence that biological invasions are facilitated by certain attributes of the invading species, for instance niche breath, and that invasive species have a broader ecological niche with respect to native ones. We designed a study to ascertain the temporal, ontogenetic, and sex differences in the niche dynamics of the American bullfrog. We sampled monthly from June 2008 to May 2009 in the state of Paraná, southern Brazil. For each individual, we gathered biometric and stomach content data. We then estimated the niche breath of the juveniles and adults, and compared it between the sexes. A total of 104 females and 77 males were sampled. Lithobates catesbeianus has a generalist diet, preying upon invertebrates and vertebrates. Even though the diet of the studied population varied seasonally, it did not differ between the sexes nor did it respond to biometric variables. Niche breadth was more restricted in the winter than in the autumn. The trophic niche of juveniles and adults did not overlap much when compared with the trophic niche overlap between males and females. Adult males and females had a considerable niche overlap, but females had a broader trophic niche than males in the winter and in the spring. These niche characteristics point to an opportunistic predation strategy that may have facilitated the process of invasion and establishment of this species in the study area.

The life expectancy of Sarconesia chlorogaster (Wiedemann, 1830) reared in artificial diet and controlled temperatures chamber set at 27±1oC, 70±10% RH and 12 hours of photophase was analysed using entropy (H). Entropy (H) was used to quantify the distribuition of deaths between ages and then quantify the impact of mortality on life expectancy. The entropy values obtained for males (H=0,245) and females (H=0,299) were intermediary between the theoretical values of H=0,5 and H=0 suggesting a tendency toward rectangular distribuitions in both sexes. The effect of mortality across ali ages on expectation of life was different at each age. For males the highest values were found between days 10 and 20 and between days 15 and 25 for females. This íindings imply that small changes in female mortality will have a greater impact on female life expectancy than will have on male expectation of life.